Supplementary material

Ni and Zn co-substituted Co(CO3)0.5OH self-assembled flowers array

for asymmetric supercapacitors

Hao Gua, Qin Zhonga*, Yiqing Zenga, Shule Zhanga, Yunfei Bub**a School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing

210094, PR China

b Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment

Technology (CICAEET), Jiangsu Key Laboratory of Atmospheric Environment Monitoring and

Pollution Control (AEMPC), UNIST-NUIST Research Center of Environment and Energy

(UNNU), School of Environment Science and Engineering, Nanjing University of Information

Science and Technology, Nanjing 210044, PR China

*Corresponding author. E-mail address: zq304@njust.edu.cn (Q. Zhong),

**Corresponding author. E-mail address: jpu441@yahoo.com (Y. Bu)

Electrochemical measurement

The electrochemical performance of the samples, the cycle voltammeter (CV),

galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy

(EIS) were performed on an electrochemical workstation (IVIUMnSTAT) by a

traditional three-electrode system, in which the prepared materials, a platinum foil and

Hg/HgO were used as the work, counter and reference electrodes, respectively. In

addition, the cycle stability was evaluated by a CT2001A LAND Cell test system.

The mass specific capacitance (C, F g-1) can be calculated by the following Eq. (1):

C= I ∆tm∆V (1)

where C (F g-1) is the mass specific capacitance, I (A) is the discharge current, ∆ t (s)

is the discharge time, ∆V (V) is the potential window, and m (g) is the mass of the

active materials.

Asymmetrical supercapacitors (ASC) with an active carbon (AC) positive

electrode and a NiZn-CoCH negative electrode with 6 M KOH electrolyte were

assembled (NiZn-CoCH //AC). The active carbon (AC, 90wt%) and polyvinylidene

fluoride (PVDF, 10 wt%) were mixed with N-methylpyrrolidinone (NMP) to obtain a

slurry, which was coated on the NF surface, and dried to obtain the AC positive

electrode. The mass loading of NiZn-CoCH and AC electrodes can be determined

according to Eq. (2):

m+¿

m−¿=C−¿×∆ V−¿

C+¿× ∆V+¿ ¿¿¿¿¿

¿ (2)

where m (g), C (F g-1) and ∆V (V) are the mass loading of electrode material, the

mass specific capacitance and the potential window. The energy density E (Wh kg -1)

and power density P (W kg-1) of ACS can be calculated by the following Eq. (3) and

(4):

E=C (∆V )2

2×3.6(3)

P=3600 E∆ t (4)

where C (F g-1) is the calculated ACS capacitance, ∆V (V) and ∆ t (s) were the

voltage range and the discharge time, respectively.

Fig. S1. SEM images of (a) the NiZn-CoCH flowers with a hydrothermal at 180 oC for 12 h, and the two control tests (b) the agglomerated block with a

hydrothermal at 120 oC for 12 h, (c) silk-like nanosheets with a hydrothermal at

180 oC for 6 h.

Fig. S2. SEM images of (a) NiZn-CoCH flowers, (b)Ni-CoCH nanosheets, (c)

CoCH nanosheets with a hydrothermal at 180 oC for 12 h.

Fig. S3. Nitrogen adsorption-desorption isotherms of (a) CoCH, (b) Ni-CoCH, (c)

NiZn-CoCH.

Fig. S4. FT-IR spectra of NiZn-CoCH.

The composition of the synthesized NiZn-CoCH was investigated by FT-IR in

the range of 500-4000 cm-1, with the results shown in Fig. S1. Two broad peaks at

3441 and 1621 cm-1 can be assigned to the -OH stretching vibration and bending

vibration of water molecules and the carbonate hydroxide. The peaks at 1361 and

1152 cm-1 arose from the asymmetrical and symmetrical stretching vibration of CO32-.

In addition, two narrow peaks at 789 and 637 cm-1 were ascribed to the in-plane and

out-of-plane bending vibration of CO32-. This FT-IR spectrum further confirmed the

NiZn-CoCH was the carbonate hydroxide.

Fig. S5. CV curves of (a) NiZn-CoCH, (d) Ni-CoCH, (g) CoCH, galvanostatic

charge-discharge curves of (b) NiZn-CoCH, (e) Ni-CoCH, (f) CoCH, specific

capacitances measured at various charge/discharge current densities of (c) NiZn-

CoCH, (f) Ni-CoCH, (i) CoCH.

Fig. S6. (a) CV curves, (b) galvanostatic charge-discharge curves, (c) gravimetric

capacitances measured at various charge/discharge current densities of active

carbon (AC).

Table S1. Comparison of the energy density and power density for the NiZn-

CoCH//AC asymmetric supercapacitor with those of cobalt based asymmetric

supercapacitors reported in recent papers.

ASCEnergy density

(Wh kg-1) maximum

Power density(W kg-1) Ref.

NiCo2O4-rGO//AC 23.32 324.9 [1]

Ni3S2/MWCNT-NC//AC 19.8 798 [2]

CoMoO4-3D graphene//AC 21.1 300 [3]

NixCo1-xLDH-ZTO//AC 23.7 284.2 [4]

C/CoNi3O4//AC 29.1 130.4 [5]

CHC/GF//C-FP 28 554 [6]

NiCo2O4//AC 14.7 175 [7]

porous Ni-Co oxide//AC 12 95.2 [8]

β-NiMoO4-CoMoO4·xH2O//AC 28 100 [9]

NiMoO4-CoMoO4·xH2O//AC 24.95 164.5 [10]

NiZn-CoCH//AC 29.58 375 this work

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